Tillerson used a pseudonym — Wayne Tracker — from 2008 to 2015, but Exxon failed to disclose that detail, the Journal reported late on Monday, citing New York Attorney General Eric Schneiderman's office.

Schneiderman is investigating whether the energy giant falsified its understanding of climate change to the public, the Journal said.

The State Department did not immediately respond to CNBC's email request sent outside office hours.